Co-interior angles are two angles on the same side of the transversal. They are the inside or interior angles and their sums add to 180. Use the two animations below to explore and test this angle relationship. Additionally, in the first animation, drag around the point "A" to manipulate the drawing.
Co-interior angles summary
Co-exterior angles are very similar to co-interior angles. They are both on the same side of the transversal but they are both on the outside or exterior. Like co-interior angles, they both add up to 1.